This invention pertains to new and improved folding structures employing a Sarrus linkage. Such folding structures are considered to be capable of being constructed so as to have a wide variety of different useful purposes.
A Sarrus linkage, or a linkage employing Sarrus motion, is a type of a folding structure in which two opposed links are connected by two different sets of connecting links, each of these sets including two separate links. The sets of connecting links are spaced from one another. In such a linkage the connecting links of each of the sets are located in edge to edge relationship and have adjacent edges which are hingedly connected to one another. The edges of the connecting links remote from the connected adjacent edges are hingedly connected to the opposed links.
Normally in a Sarrus linkage the opposed links and the connecting links are constructed so that the opposed links are parallel to one another and will move in parallel planes as any part of the Sarrus linkage is moved with respect to the remainder of the linkage. The opposed links, however, need not move in parallel planes in a Sarrus linkage. Such a linkage can be constructed so that as it is operated the opposed links move generally toward and away from one another about an axis in a manner which can be compared to the way that the pages of a book move as they are turned.
It is considered that it is now reasonably established that a wide variety of different utilitarian folding structures can be created utilizing a Sarrus linkage. It is not considered that an understanding of the invention requires a detailed discussion of such structures. It is considered, however, that many such prior utilitarian structures employing a Sarrus linkage are relatively disadvantageous in some specific applications because of the problems and complications involved in manipulating the linkage between a generally expanded, open or unfolded configuration and a generally compact or folded configuration. While such relative motion can be created by physically engaging a single part of a Sarrus linkage and moving that part relative to the remainder of the linkage, in certain applications this type of construction is relatively disadvantageous.
As a result of the preceding consideration it is considered that there is a need for new and improved folding structures employing a Sarrus linkage. It is considered that this need is particularly significant in connection with the construction of folding structures such as step stool or saw horse type structures, folding tables or benches and the like. It will be recognized that a wide variety of different types of folding step stools, folding tables, benches and related structures have been known and used and have proven to be very satisfactory and practical. It is not considered necessary to discuss these prior folding structures. It is believed that many such structures have been relatively undesirable in one or more regards because they have not utilized a linkage in an effective manner so as to achieve a comparatively simple type structure capable of being easily and conveniently constructed having advantageous physical folding characteristics.